1. Field of the Invention
The present invention relates to a backlight module, and more specifically, to a backlight module using a plurality of point light source generators as light sources.
2. Description of the Prior Art
Backlight modules are one of the most important parts of liquid crystal displays (LCD), which are widely used in digital cameras, personal digital assistants (PDAs), computer monitors, and flat panel televisions. Generally, a backlight module is installed under a display panel and provides a uniform light to the display panel utilizing a light source and a diffusing plate, and controls pixel electrodes on the display panel to display images. Backlight modules can be divided into a direct type with a light source means under a display panel, and an edge light type with a light source on the edge of the display panel.
Please refer to FIG. 1 showing the structure of a conventional direct type backlight module 10. As shown in FIG. 1, the backlight module 10 is installed under a display panel 12 and includes at least one light source generator 14, a diffusing sheet 16 installed between the light source generator 14 and the display panel 12, a diffusing plate 18 installed between the light source generator 14 and the diffusing sheet 16, and a reflecting plate 20 fixed on a housing 22 under the light source generator 14.
The light source generator 14 is for providing a light source to the display panel 12, the reflecting plate 20 is for reflecting the light generated by the light source generator 14 upward to increase efficiency of the light source generator and provide a brighter output. The diffusing plate 18 is for scattering the light generated by the light source generator 14 to the diffusing sheet 16, and the diffusing sheet 16 can further scatter the light passing through it to provide uniform light to the display panel 12. The housing 22 installed under the reflecting plate 20 and covering the reflecting plate 20 is for fixing the diffusing plate 18, the reflecting plate 20, and the light source generator 14. Generally, at least one prism sheet 24 is installed above the diffusing sheet 16 to further modify the differences of light intensity so that the light received by the display panel 12 has a more uniform light intensity distribution. The quantity and the arrangement of the prism sheet(s) 24 can be modified according to the requirements.
The light source generator 14 in the conventional backlight module 10 is composed of at least one cold cathode fluorescent lamp (CCFL). In order to fulfill the requirements of high brightness, the light source generator 14 in the conventional backlight module 10 is installed in a narrow space. The narrow space often results in the heat generated during operation not being successfully dissipated. When the CCFL is operated for a long time, the light tubes may overheat. Additionally, when the temperature of the light tubes is over a normal range of 70° C.˜80° C., not only the brightness of the backlight module and the life of the light tubes decrease but the high temperature may cause low display quality (e.g. poor contrast) of the display panel 12. Additionally, electromagnetic interference occurs when the number of CCFL light tubes exceeds a typical level, limiting the usage of LCDs (e.g. unable to use in an aircraft).